*how to extract numeric part of a string
*http://www.stata.com/statalist/archive/2002-12/msg00353.html
program define extrnum
version 7
syntax varlist(max=1), gen(str)
local maxlen: type `varlist'
*disp "`maxlen'"
local maxlen=substr("`maxlen'",4,.)
*disp `maxlen'
tempvar work
qui gen str1 `work'=""
forvalues i=1/`maxlen' {
 qui replace `work'=`work'+substr(`varlist',`i',1) if real(substr(`varlist',`i',1))<.
}
*gen `gen'="`work'"
gen `gen'=real(`work')
end
/*
*Warning: you should check to make sure that email doesn't split the long
line in the forvalues loop (there should be just a single command in the
loop).

for your example, the syntax would be:

extrnum Var_source, gen(Var_target)
*/
